the TIMI Investigators* Background. The influence of coronary collateral vessels on infarct size in humans remains controversial, partly because no previous study has examined the impact of collaterals present at the onset of acute myocardial infarction on infarct size.

The dependence of vascular relaxation on an intact endothelium and the relationship between relaxation and cyclic GMP accumulation were determined in coronary arteries isolated from cardiac transplantation patients with or without coronary atherosclerosis. In nonatherosclerotic arteries, the endothelium-dependent agent acetylcholine produced concentration-related relaxations. In atherosclerotic arteries, endothelium-dependent relaxations were abolished with acetylcholine, partly suppressed with substance P and histamine, and completely preserved with the ionophore A23187. In these arteries, the endothelium-independent agent nitroglycerin remained fully active. Accumulation of cyclic GMP in atherosclerotic strips was suppressed with acetylcholine but unattenuated with A23187 and nitroglycerin. In aortas from rabbits with diet-induced atherosclerosis, there was likewise an impaired cholinergic relaxation and cyclic GMP accumulation in the presence of preserved responses to A23187 and nitroglycerin. The results demonstrate that impaired cholinergic responses in atherosclerotic arteries reflect a muscarinic defect and not an inability of endothelium to release endothelial factor or smooth muscle to respond to it.

The CK-MB subform assay alone or in combination with a troponin reliably triages patients with chest pain and should lead to improved therapy and reduced cost.

r-PA given as a double bolus of 10 + 10 MU achieves more rapid, complete, and sustained thrombolysis of the infarct-related artery than standard-dose TPA, without an apparent increased risk of complications. This was associated with improved global and regional left ventricular function at hospital discharge.

To examine whether alterations in right ventricular filling dynamics occur with increasing age and to compare right and left ventricular filling in normal subjects, pulsed Doppler echocardiographic studies were performed at the tricuspid and mitral anuli in 50 normal volunteers (23 males and 27 females) with an age range of 5-66 years. An age-related decrease in peak early filling velocity, increase in peak late velocity, and augmentation in the late/early ratio of peak velocities at the tricuspid anulus were observed (r= -0.68, 0.63, and 0.84, respectively). Significant correlations were also found between age and first third, first half, and atrial filling fractions (r=-0.60, -0.72, and 0.69, respectively Methods Subject PopulationThe population consisted of 50 normal volunteers (23 males and 27 females) with an age range of 5-66 years (mean, 37+15 years) who met all the following criteria: the individuals were asymptomatic, had no risk factors for coronary artery disease, and had neither history nor evidence of systemic hypertension or cardiovascular, pulmonary, or systemic disease. All subjects had a supine blood pressure below 150/90 mm Hg and normal physical examination, electrocardiogram, and two-dimensional and Doppler echocardiographic studies. Echocardiographic and Doppler StudiesTwo-dimensional and Doppler echocardiographic studies were performed by using an ultrasound system (model 77020AC, Hewlett-Packard Co., Palo Alto, Calif., or Ultramark 8, Advanced Technology Laboratories, Bothell, Wash.) equipped with 3.5-, 2.5-, or 2.25-MHz transducers and recorded on 1/2-in. videotape. Echocardiographic images were obtained from the parasternal and apical windows, with the patient in the left lateral recumbent position.Pulsed Doppler studies were performed by using the parasternal and apical windows.